Triggering updates in Orchard

I've uploaded a widget (1.0) already to the Orchard Gallery and have since made updates to that widget. Now when I upload this new version of my widget (1.2), I see 1.2 in the Gallery but on my test site I still have (1.0) but there's no message
telling me that I should update. I did not make any database changes but I did put in a blank UpdateFrom1() function in my migrations.cs file in hope that this would trigger the message but had no luck there either.

What would be the best way to let someone know that there is a new version of my widget online?

You need to actually install that new version on your site, and then it will prompt you to upgrade the database. At this moment there is no facility to upgrade a module other than removing its directory and installing the new one but that is coming in 1.1
if all goes well.